Moldboards, such as are conventionally used for snow and ice removal, are well known in the art. Moldboards come in a wide variety of shapes and sizes depending upon the intended use. Some moldboards are relatively small and light and are intended to be mounted on a light domestic truck, i.e., a "pickup truck". Other moldboards are of significantly larger size and weight and are intended for municipal or commercial use. These larger moldboards are typically mounted on large trucks which may also be used for spreading sand or salt.
A concern when using a moldboard to remove snow or ice is how to deal with obstructions occurring on the surface being plowed. Some surfaces are considerably rougher than others and may have numerous obstructions. Objects such as grates and manhole covers, rocks, curbs, etc., provide impediments to the removal of ice and snow and may damage the lower edge of the moldboard. In addition, if an obstruction is large enough, the obstruction may cause significant damage to the moldboard and may bring the vehicle used in the plowing operation to an abrupt halt which may result in injury to the vehicle operator.
Various arrangements have been provided along the bottom edge of a moldboard to deal with obstructions. These arrangements are commonly called "trip mechanisms" and are provided to avoid damage to the moldboard and to the vehicle carrying the moldboard.
A representative trip mechanism is described in U.S. Pat. No. 5,079,866, of Gene Farrell, which was issued on Jan. 14, 1992. In the '866 patent, the trip mechanism has a hinged cutting edge along the bottom of the moldboard with two pivotally mounted linkage members and a trip return spring provided on each end of the moldboard to resiliently maintain the orientation of the cutting edge of the moldboard relative to the surface being plowed. If the cutting edge of the moldboard should encounter an obstruction, the pivotally mounted linkage members act on the plowshoe to cause the moldboard to raise and clear the obstruction. After the moldboard has passed beyond the obstruction, the trip return springs cause the cutting edge to return to its normal orientation and the moldboard returns to its initial position.
A trip mechanism such as is described in the '866 patent or other trip mechanisms provided along the bottom edge of a moldboard used in snow removal provide significant protection against damage to the moldboard or to the surface being plowed. However, the need exists for different or for additional protection for moldboards and for the surfaces being plowed especially in the event that a moldboard should encounter an obstruction above the cutting edge.
Such different or additional protection against obstructions must be economical in design and construction as well as reliable in operation. Preferably, such protection for moldboards against obstructions will have relatively few moving parts and will be resistant to damage from rust or from low temperatures because of the environment in which such mechanism must function.
In view of the above background information, it is an object of the present invention to provide a mounting arrangement for a moldboard which provides protection against obstructions encountered during plowing.
A further object of the present invention is to provide a mounting arrangement for a moldboard providing an improved trip mechanism of high reliability and low complexity.
It is another object of the present invention to provide a mounting arrangement for a moldboard having an improved trip mechanism requiring low maintenance and which is suitable for use in a wet and cold environment.
An additional object of the present invention is to provide a mounting arrangement for a moldboard having an improved trip mechanism capable of preventing or significantly reducing damage to the moldboard or to the vehicle or to the operator when obstructions are encountered by the moldboard during plowing.
The above objects as well as other objects not specifically mentioned are accomplished by a mounting arrangement for a moldboard in accordance with the present invention. The mounting arrangement for a moldboard according to the present invention comprises truss means for connecting the moldboard to a vehicle and arm means for pivotally mounting the moldboard on the truss means. In addition, means are provided for resiliently connecting the arm means to the truss means. In the preferred embodiment of the present invention, the truss means includes a mounting member extending longitudinally along the moldboard, with the arm means including first and second arm members received at the ends of the mounting member. In addition, the means for resiliently connecting the arm means to the truss means preferably includes a urethane member provided at each of the first and second arm members between the arm members and the mounting member. Preferably, the mounting member is square in cross-section and hollow along the entire length of the mounting member to provide openings at each end of the mounting member with the urethane members being square in cross-section and configured to be snugly received within the openings in the mounting member. Preferably, each of the first and second arm members includes a shaft extending perpendicularly from said arm member with one of the urethane members being bound to the shaft of each of the arm members. In the preferred embodiment, a cam member is provided on each shaft to limit the extent of angular movement of the arm member and the moldboard about the mounting member.
In an alternative embodiment, each of the shafts of the first and second arm members is square in cross section whereby pivoting of the arm members and the moldboard about the mounting member causes the urethane members to be compressed inside the mounting member when the moldboard encounters an obstruction.